Dental caries and enamelin haplotype

Genetic variations in exon 10 of ENAM and their association with early childhood caries

OBJECTIVE

Enamelin is the largest enamel matrix protein encoded by the ENAM gene. The primary purpose of this study was to identify genetic variants in ENAM exon 10 that can alter susceptibility to early childhood caries (ECC).

METHODS

This case-control study included 248 children aged 3-6 years, with 124 children diagnosed with ECC in the case group and 124 children without caries in the control group. Questionnaires were used to record demographic data, socioeconomic status, hygienic practices, and feeding practices, and a 24-h diet diary was kept. Seven polymorphisms (rs7671281, rs1738668322, rs3796703, rs3796704, rs759376039, rs775159311, and rs1738678483) in ENAM exon 10 were sequenced.

RESULTS

The heterozygous CT genotype of rs7671281 was significantly more common in the case group compared to the control group (odds ratio [OR], 6.1765; 95% confidence interval [CI], 2.05-18.58; P = 0.0006). Under the dominant model, the TT genotype of rs7671281 was significantly more common in the control group (OR, 6.47; 95% CI, 2.15-19.39; P < 0.001). The AG genotype of rs3796704 was significantly more common in the case group than in the control group (OR, 5.705; 95% CI, 1.60-20.25; P = 0.006). Under the dominant model, the GG genotype of rs3796704 was significantly more common in children without caries than in children with caries (OR, 6.84; 95% CI, 1.96-23.90; P < 0.001).

CONCLUSIONS

The C allele of rs7671281 and the A allele of rs3796704 can increase susceptibility to ECC.

Single nucleotide polymorphisms of enamel formation genes and early childhood caries - systematic review, gene-based, gene cluster and meta-analysis

Introduction

Genetic polymorphisms of genes regulating amelogenesis can alter susceptibility to Early Childhood Caries (ECC). This systematic review aims to analyze associations between single-nucleotide polymorphisms of enamel formation genes and ECC.

Methods

Search was conducted across PUBMED, CINAHL, LILACS, SCOPUS, EMBASE, Web of Science, Genome-Wide Association Studies databases from January 2003 to September 2022. This was supplemented by hand search. Totally 7124 articles were identified and 21 articles that satisfied the inclusion criteria proceeded to data extraction. Quality assessment was done using the Q-Genie tool.

Results

Quantitative synthesis revealed that homozygous genotype AA of rs12640848 was significantly higher in children with ECC with an odds ratio of 2.36. Gene-based analysis revealed significant association between six variants of AMBN, four variants of KLK4, two variants of MMP20, and a single variant of each of MMP9 and MMP13 genes and ECC. The Bonferroni corrected-log10 P value of amelogenesis gene Cluster was 2.25 (0.05/88 = 5.6 × 10^-4). Search Tool for Retrieval of Interacting Genes and Proteins plot constructed to comprehend the protein-protein interaction revealed the presence of four functional clusters. Gene function prediction using Multiple Association Network Integration Algorithm revealed that physical interaction between these genes was 69.3%.

Conclusion

Polymorphisms of genes regulating amelogenesis can influence the susceptibility to ECC. AA genotype of rs12640848 may increase the susceptibility to ECC. Gene-based analysis revealed a significant association between multiple polymorphisms of genes regulating amelogenesis and ECC.

Analysis of ENAM gene single-nucleotide polymorphism rs3796704 with caries susceptibility in young adult Tamil population

Background:

Dental caries is as primeval as humanity, but still, investigations are undergoing regarding the etiopathogenesis behind this multifactorial disease. Genetics is known to play a vital role in the etiology behind dental caries in addition to environmental and socioeconomic factors. Genetic variations like single-nucleotide polymorphisms (SNPs) were extensively studied in the past decade to portray the etiopathogenesis contributing to dental caries.

Aim:

This investigation was undertaken to analyze the ENAM gene SNP rs3796704 with caries susceptibility in ethnic young adult Tamil population of India.

Materials and Methods:

Out of 370 patients included, 215 patients belonged to the high caries group (Decayed, Missing and Filled Tooth [DMFT] ≥2) and 155 patients belonged to the low caries group (DMFT ≤ 1). DNA was extracted from the blood of all the individuals. SNP genotyping was performed utilizing tetra-primer amplification refractory mutation system–polymerase chain reaction with specific primers.

Results:

The genotyping results showed that there were no differences in allelic (P = 0.114) and genotypic frequencies (P = 0.159) between the high caries and low caries groups.

Conclusion:

Future studies can be conducted in larger samples and different ethnicities around the globe to analyze the role played by SNPs of enamel formation genes in cariogenesis.

Prediction of Early Childhood Caries Based on Single Nucleotide Polymorphisms Using Neural Networks

Background: Several genes and single nucleotide polymorphisms (SNPs) have been associated with early childhood caries. However, they are highly age- and population-dependent and the majority of existing caries prediction models are based on environmental and behavioral factors only and are scarce in infants. Methods: We examined 6 novel and previously analyzed 22 SNPs in the cohort of 95 Polish children (48 caries, 47 caries-free) aged 2–3 years. All polymorphisms were genotyped from DNA extracted from oral epithelium samples. We used Fisher’s exact test, receiver operator characteristic (ROC) curve and uni-/multi-variable logistic regression to test the association of SNPs with the disease, followed by the neural network (NN) analysis. Results: The logistic regression (LogReg) model showed 90% sensitivity and 96% specificity, overall accuracy of 93% (p < 0.0001), and the area under the curve (AUC) was 0.970 (95% CI: 0.912–0.994; p < 0.0001). We found 90.9–98.4% and 73.6–87.2% prediction accuracy in the test and validation predictions, respectively. The strongest predictors were: AMELX_rs17878486 and TUFT1_rs2337360 (in both LogReg and NN), MMP16_rs1042937 (in NN) and ENAM_rs12640848 (in LogReg). Conclusions: Neural network prediction model might be a substantial tool for screening/early preventive treatment of patients at high risk of caries development in the early childhood. The knowledge of potential risk status could allow early targeted training in oral hygiene and modifications of eating habits.

Biomarkers for Lifetime Caries-Free Status

The purpose of this study was to address the hypothesis that extreme outcomes of dental caries, such as edentulism or prematurely losing permanent teeth are associated with genetic variation in enamel-formation genes. After scanning 6206 individuals, samples of 330 were selected for this study. Tested phenotypes included patients who were edentulous by age 30, patients with missing first molars by age 30, patients with missing second molars by age 30, and caries-free patients. Fourteen single nucleotide polymorphisms were genotyped by TaqMan chemistry. The analyses of each phenotype were performed using the software PLINK with an alpha of 0.05. Nominal associations were found between rs12640848 in enamelin (p = 0.05), rs1784418 in matrix metallopeptidase 20 (p = 0.02), and rs5997096 in the tuftelin interacting protein 11 and being caries-free at the age of 60. When combining patients that were missing both first mandibular molars and missing both second mandibular molars, no associations were found. Matrix metallopeptidase 20, and tuftelin interacting protein 11 also showed trends for association with being caries-free. Genetic variation in TFIP11, MMP20, and ENAM may have a protective effect increasing the chances of individuals preserving their teeth caries-free over a lifetime.

Genes in the pathway of tooth mineral tissues and dental caries risk: a systematic review and meta-analysis

OBJECTIVES

To perform a systematic review of the literature, investigating the influence of tooth mineral tissues genes on dental caries.

MATERIALS AND METHODS

Five databases were searched. Only human studies with cross-sectional, longitudinal, and case-control design were included. Meta-analysis was performed for each polymorphism, providing allele and genotype estimates. A meta-analysis was performed, pooling several polymorphisms for each gene. A Funnel Plot and Egger's test were also performed.

RESULTS

A total of 1124 records were found. Of these, 25 papers were included in the systematic review and 18 in the meta-analysis. Most of the studies (52%) were of medium quality. With regard to the allele analysis, the T allele of rs134136 (TFIP11) (OR 1.51; 95%CI 1.02-2.22) showed an association with high experience of caries and the summarization of polymorphisms investigated in the TFIP11 gene, after exclusion of SNP linkage disequilibrium, showed an association with caries experience (OR 1.64; 95%CI 1.08-2.50). An analysis of the homozygous genotype did not show any significant association. The pooled SNPs of AMBN showed associations with caries (OR 0.45; 95%CI 0.29-0.72). The pooled polymorphisms of AMELX were associated with caries experience (OR 1.78; 95%CI 1.23-2.56). In the analysis of the homozygous genotype, no SNP showed a significant association. Egger's test showed no significant publication bias for all models (p > 0.05).

CONCLUSION

The present findings showed that the genes TFIP11, AMBN, and AMELX play an important role in dental caries.

CLINICAL RELEVANCE

Several single nucleotide polymorphisms related to the genes in the formation of tooth mineral are linked to the occurrence of dental caries, and these genes have proved to be important for an explanation of differences in the risk of dental caries.

ENAM mutations and digenic inheritance

BACKGROUND

ENAM mutations cause autosomal dominant or recessive amelogenesis imperfecta (AI) and show a dose effect: enamel malformations are more severe or only penetrant when both ENAM alleles are defective.

METHODS

Whole exome sequences of recruited AI probands were initially screened for mutations in known AI candidate genes. Sanger sequencing was used to confirm sequence variations and their segregation with the disease phenotype. The co-occurrence of ENAM and LAMA3 mutations in one family raised the possibility of digenic inheritance. Enamel formed in Enam+/+ Ambn+/+ , Enam+/- , Ambn+/- , and Enam+/- Ambn+/- mice was characterized by dissection and backscattered scanning electron microscopy (bSEM).

RESULTS

ENAM mutations segregating with AI in five families were identified. Two novel ENAM frameshift mutations were identified. A single-nucleotide duplication (c.395dupA/p.Pro133Alafs*13) replaced amino acids 133-1142 with a 12 amino acid (ATTKAAFEAAIT*) sequence, and a single-nucleotide deletion (c.2763delT/p.Asp921Glufs*32) replaced amino acids 921-1142 with 31 amino acids (ESSPQQASYQAKETAQRRGKAKTLLEMMCPR*). Three families were heterozygous for a previously reported single-nucleotide ENAM deletion (c.588+1delG/p.Asn197Ilefs*81). One of these families also harbored a heterozygous LAMA3 mutation (c.1559G>A/p.Cys520Tyr) that cosegregated with both the AI phenotype and the ENAM mutation. In mice, Ambn+/- maxillary incisors were normal. Ambn+/- molars were also normal, except for minor surface roughness. Ambn+/- mandibular incisors were sometimes chalky and showed minor chipping. Enam+/- incisor enamel was thinner than normal with ectopic mineral deposited laterally. Enam+/- molars were sometimes chalky and rough surfaced. Enam+/- Ambn+/- enamel was thin and rough, in part due to ectopic mineralization, but also underwent accelerated attrition.

CONCLUSION

Novel ENAM mutations causing AI were identified, raising to 22 the number of ENAM variations known to cause AI. The severity of the enamel phenotype in Enam+/- Ambn+/- double heterozygous mice is caused by composite digenic effects. Digenic inheritance should be explored as a cause of AI in humans.

Dental caries: Genetic and protein interactions

OBJECTIVE

To present a genetic and protein interaction analysis associated with dental caries.

MATERIAL AND METHODS

The first step was to conduct a systematic literature review (SLR) through an electronic database search. Case-controls that reported associations between genes and dental caries were the main type of study design used as inclusion criteria, retrieved from the PubMed and the Virtual Health Library databases, comprising the chronological range from 1982 to 2017. The SLR was guided by PRISMA protocol and the methodological quality of the studies was established through Newcastle-Ottawa Scale (NOS). In the second step, the String Protein Interaction (SPI) approach was used to analyze protein interaction (by esyN software) and also the Ingenuity Pathway Analysis (IPA) to check biological pathways associated with dental caries genes.

RESULTS

A total of 51 articles were included to perform this SLR, describing a number of 27 genes associated with dental caries development. At the genetic level, 23 genes have at least one other gene with which they interact. The genes TUFT1, VDR, TFIP11, LTF, HLA-DRB1, MMP2, MMP3 and MUC5B were shown to be connected in interactive networks by at least 10 other genes.

CONCLUSION

It is essential to apprehend the multifactorial pattern of inheritance in human disease. This study presents pathways which may be directly correlated with several dental caries phenotype and this contributes to a better understanding of this disease, opening up a wider range of biotechnology options for its effective control in the future.

Host genetics role in the pathogenesis of periodontal disease and caries

BACKGROUND

This study aimed to produce the latest summary of the evidence for association of host genetic variants contributing to both periodontal diseases and caries.

MATERIALS AND METHODS

Two systematic searches of the literature were conducted in Ovid Medline, Embase, LILACS and Cochrane Library for large candidate gene studies (CGS), systematic reviews and genome-wide association studies reporting data on host genetic variants and presence of periodontal disease and caries.

RESULTS

A total of 124 studies were included in the review (59 for the periodontitis outcome and 65 for the caries outcome), from an initial search of 15,487 titles. Gene variants associated with periodontitis were categorized based on strength of evidence and then compared with gene variants associated with caries. Several gene variants showed moderate to strong evidence of association with periodontitis, although none of them had also been associated with the caries trait.

CONCLUSIONS

Despite some potential aetiopathogenic similarities between periodontitis and caries, no genetic variants to date have clearly been associated with both diseases. Further studies or comparisons across studies with large sample size and clear phenotype definition could shed light into possible shared genetic risk factors for caries and periodontitis.

Association between ENAM polymorphisms and dental caries in children

Aim

Dental enamel, the most rigid biological tissue of the tooth known to mankind, is the most integral and fundamental part of the tooth. Enamel matrixes compile 5% of Enamelin peptides and at the time of tooth development, they are considered to effect the formation and elongation of enamel crystallites. ENAM plays critical role in enamel formation. Any changes in ENAM may affect the thickness of enamel and may lead to dental caries. The present study is aimed to evaluate the association of ENAM gene polymorphisms and susceptibility of dental caries development risk.

Material and methods

The present study was carried out on 168 South Indian children, children’s with dental caries were included in study. Written consent was taken from their parents/guardians. Additionally 193 healthy individuals were enrolled as controls. Sampling was done after dental examination of the individuals. Three ENAM gene single nucleotide polymorphisms (SNPs) were rs7671281, rs3796704 and rs12640848 was genotyped to check their role in susceptibility of dental caries development risk.

Results

Out of three SNPs rs7671281 showed statistically significant risk association with dental caries susceptibility in this ethnic population at heterozygous allele CT (OR: 1.939, p = .01865) and with minor allele T (OR: 1.451, p = .001292). SNP rs3796704 showed significant protective association with dental caries in Indian population at heterozygous allele GA (OR: 0.409, p = .0192) and with minor allele A (OR: 0.645, p = .00875). SNP rs12640848 showed significant protective association with dental caries in Indian population at heterozygous allele AG (OR: 3.041, p = .00642) and with minor allele G (OR: 1.478, p = .02184). Preliminary insilico analysis also showed that rs7671281 (Ile648Thr) amino acid change will cause the structural and functional changes in ENAM protein.

Conclusions

In the present study significant association was observed between ENAM gene SNP rs7671281 and dental caries susceptibility in South Indian children. These results suggested that ENAM gene variants may contribute to dental caries in children.

Lack of association between ENAM gene polymorphism and dental caries in primary and permanent teeth in Czech children

OBJECTIVES

The enamelin gene (ENAM) polymorphism (rs12640848) was recently associated with dental caries in primary teeth in Polish children. The aims of the present study were to prove this association in primary dentition and to find a possible effect of this variant on caries development in permanent dentition in Czech children.

MATERIALS AND METHODS

This study comprised 905 Czech children. Totally, 187 children aged 2-6 years with primary dentition [78 healthy subjects (with decayed/missing/filled teeth, dmft = 0) and 109 patients with early childhood caries (ECC; dmft ≥ 1)] were included in this case-control study. In addition, 177 subjects aged 13-15 years without caries (DMFT = 0) and 541 children with dental caries (DMFT ≥ 1) in permanent dentition were selected from the ELSPAC study. Genotype determination of the ENAM polymorphism (rs12640848) was based on the TaqMan method.

RESULTS

No significant differences in the allele or genotype frequencies between the caries-free children and those affected by dental caries were observed in both primary and permanent dentitions.

CONCLUSIONS

Lack of association between the ENAM polymorphism (rs12640848) and dental caries in Czech children was detected.

CLINICAL RELEVANCE

Although ENAM is considered as a candidate gene for dental caries, the presence of the ENAM variant (rs12640848) cannot be used as a risk factor of this multifactorial disease in the Czech population.

Variation in Enamel Formation Genes Influences Enamel Demineralization In Vitro in a Streptococcus mutans Biofilm Model

Genetic studies have shown that variations in enamel formation genes are associated with caries susceptibility. The aim of this study was to test in vitro whether variants in these genes are associated with dental enamel demineralization in a Streptococcus mutans biofilm model. DNA and enamel samples were obtained from 213 individuals. DNA was extracted from saliva, and 16 single nucleotide polymorphisms were analyzed. The physical and chemical properties of sound enamel samples and the mineral loss and the lesion depth of the demineralized enamel samples under cariogenic challenge were analyzed. Microhardness, enamel chemicals, mineral loss and demineralization depth were compared between different genotypes at each single nucleotide polymorphism. The GG genotype of TUFT1 (rs17640579) and the GT genotype of MMP20 (rs1612069) exhibited increased microhardness (p = 0.044 and 0.016, respectively). The GG genotype of AMBN (rs7694409) had a higher magnesium level, while the CT genotype of TFIP11 (rs2097470) had a lower magnesium level (p = 0.044 and 0.046, respectively). The GT genotype of MMP20 (rs1612069) had a higher calcium level (p = 0.034). The GG genotype of AMBN (rs13115627), the AG genotype of ENAM (rs12640848) and the AA genotype of MMP20 (rs2292730) had a lower phosphorus level (p = 0.012, 0.006, and 0.023, respectively). The GG genotype of AMBN (rs13115627) was also associated with a higher calcium-phosphorus ratio (p = 0.034). Individuals with the CC genotype of TFIP11 (rs134143) exhibited significantly more mineral loss (p = 0.011) and a deeper lesions (p = 0.042). Individuals with the TT genotype of TFIP11 (rs2097470) had more mineral loss (p = 0.018). Individuals with the GG genotype of TUFT1 (rs17640579) exhibited a shallower demineralization depth (p = 0.047). Individuals with the GT genotype of MMP20 (rs1612069) exhibited a shallower demineralization depth (p = 0.042). Individuals with the GG genotype of ENAM (rs12640848) exhibited less mineral loss (p = 0.01) and a shallower demineralization depth (p = 0.03). Genetic variations in TFIP11, TUFT1, MMP20, and ENAM influenced enamel demineralization in a Streptococcus mutans biofilm model.

Neanderthal and Denisova tooth protein variants in present-day humans

Environment parameters, diet and genetic factors interact to shape tooth morphostructure. In the human lineage, archaic and modern hominins show differences in dental traits, including enamel thickness, but variability also exists among living populations. Several polymorphisms, in particular in the non-collagenous extracellular matrix proteins of the tooth hard tissues, like enamelin, are involved in dental structure variation and defects and may be associated with dental disorders or susceptibility to caries. To gain insights into the relationships between tooth protein polymorphisms and dental structural morphology and defects, we searched for non-synonymous polymorphisms in tooth proteins from Neanderthal and Denisova hominins. The objective was to identify archaic-specific missense variants that may explain the dental morphostructural variability between extinct and modern humans, and to explore their putative impact on present-day dental phenotypes. Thirteen non-collagenous extracellular matrix proteins specific to hard dental tissues have been selected, searched in the publicly available sequence databases of Neanderthal and Denisova individuals and compared with modern human genome data. A total of 16 non-synonymous polymorphisms were identified in 6 proteins (ameloblastin, amelotin, cementum protein 1, dentin matrix acidic phosphoprotein 1, enamelin and matrix Gla protein). Most of them are encoded by dentin and enamel genes located on chromosome 4, previously reported to show signs of archaic introgression within Africa. Among the variants shared with modern humans, two are ancestral (common with apes) and one is the derived enamelin major variant, T648I (rs7671281), associated with a thinner enamel and specific to the Homo lineage. All the others are specific to Neanderthals and Denisova, and are found at a very low frequency in modern Africans or East and South Asians, suggesting that they may be related to particular dental traits or disease susceptibility in these populations. This modern regional distribution of archaic dental polymorphisms may reflect persistence of archaic variants in some populations and may contribute in part to the geographic dental variations described in modern humans.

Single Nucleotide Polymorphism in the Aetiology of Caries: Systematic Literature Review

Recent progress in the field of molecular biology and techniques of DNA sequence analysis allowed determining the meaning of hereditary factors of many common human diseases. Studies of genetic mechanisms in the aetiology of caries encompass, primarily, 4 main groups of genes responsible for (1) the development of enamel, (2) formation and composition of saliva, (3) immunological responses, and (4) carbohydrate metabolism. The aim of this study was to present current knowledge about the influence of single nucleotide polymorphism (SNP) genetic variants on the occurrence of dental caries. PubMed/Medline, Embase, and Cochrane Library databases were searched for papers on the influence of genetic factors connected with SNP on the occurrence of dental caries in children, teenagers, and adults. Thirty original papers written in English were included in this review. Study groups ranged from 30 to 13,000 subjects. SNPs were observed in 30 genes. Results of the majority of studies confirm the participation of hereditary factors in the aetiology of caries. Three genes, AMELX, AQP5, and ESRRB, have the most promising evidence based on multiple replications and data, supporting a role of these genes in caries. The review of the literature proves that SNP is linked with the aetiology of dental caries.

Significance of genetic variations in developmental enamel defects of primary dentition in Polish children

OBJECTIVES

The aim of the study was to reveal the association between developmental defects of enamel (DDE) and single nucleotide polymorphisms (SNPs) in the ENAM, AMELX, AMBN, TUFT1, and TFIP11 genes.

MATERIAL AND METHODS

The molecular analysis was carried out in 52 children, aged 10-42 months, from four nursery schools situated in the region of Poznan, Poland (26 individuals with hypomineralization and/or hypoplasia of enamel - "cases" and 26 unaffected children - "controls"), chosen from 262 individuals that had prior dental examination. Six selected SNP variants (rs17878486 in AMELX, rs4694075 in AMBN, rs3796704 in ENAM, rs134136 and rs5997096 in TFIP11, and rs3790506 in TUFT1) were genotyped by the TaqMan probes assay. Genotype and allele frequencies were calculated, and a standard chi-squared analysis was used to test for deviation from Hardy-Weinberg equilibrium. The association between genetic variations and developmental defects of enamel was assessed by the Fisher's exact test and p ≤ 0.05 was considered statistically significant.

RESULTS

Statistically significant positive correlations were found between the rare T allele (p = 0.005) and the TT genotype (p = 0.0052) for rs17878486 in AMELX and occurrence of developmental enamel defects in primary dentition of children. For rs4694075 in AMBN, a higher incidence of the rare T allele (p = 0.0157) was observed in controls compared to DDE cases, whereas the wild-type CC homozygote was more frequent in DDE cases than in controls (p = 0.0062).

CONCLUSIONS

The study showed that the single nucleotide polymorphisms in the AMELX and AMBN genes may be genetic variants that contribute to developmental defects of enamel in primary dentition of children.

CLINICAL RELEVANCE

The single nucleotide polymorphisms of enamel formation genes may increase the risk for developmental defects of enamel (DDE) occurrence in primary dentition in children.

The association of Enamelin, Lactoferrin, and Tumour necrosis factor alpha gene polymorphisms with high caries susceptibility in Chinese children under 4 years old

OBJECTIVE

The aim of this study was to assess the role of ENAM rs3796703, LTF rs1126478, and TNF-α rs1800629 in high caries susceptibility.

DESIGN

The present case-control study included 1005 unrelated children under 4 years old: 505 with severe caries (dmft index ≥4) and 500 who were caries-free (dmft index=0 and without white-spot lesions). Questionnaires were obtained from parents and gardians about the children's diet and oral behavioural habits. All the children received dental examinations and oral swabbing for human genomic DNA collection. ENAM rs3796703, LTF rs1126478, and TNF-α rs1800629 were genotyped by Sanger sequencing.

RESULTS

The frequency of the ENAM rs3796703T allele (6.7% in the caries group and 4.2% in the caries-free group), CT genotype (12.7% in the caries group and 8.4% in the caries-free group), TNF-α rs1800629 A allele (4.8% in the caries group and 6.8% in the caries-free group), and AG genotype (8.7% in the caries group and 13.2% in the caries-free group) were significantly different between the caries and caries-free groups (p<0.05). No significant difference was found in the LTF rs1126478 allele frequency and genotype distribution between the two groups. The ENAM rs3796703 CT genotype increased caries susceptibility by 60.9% compared to the CC genotype (β=0.746, OR=1.609), and the TNF-α rs1800629 AG genotype reduced caries susceptibility by 47.4% compared to the GG genotype (β=-0.642, OR=0.526). In terms of habits covariates, prolongation of night feeding time by 1 month increased caries susceptibility by 3.3% (β=0.033, OR=1.033); additionally, sweets and acidic drinks consumption 1-2 times per day increased caries susceptibility by 218.2% (β=1.158, OR=3.182), and consumption 3 or more times pe/r day increased susceptibility by 883.5% (β=2.286, OR=9.835) compared to non-consumption. Topical fluoride application decreased caries susceptibility by 43.0% (β=-0.562, OR=0.570).

CONCLUSIONS

The ENAM and TNF-α genes are likely associated with caries experience in Chinese children. The ENAM rs3796703 CT genotype might be involved in caries susceptibility, while TNF-α rs1800629 AG genotype might be involved in caries protection.

Chronic Exposure to Bisphenol A Exacerbates Dental Fluorosis in Growing Rats

Enamel defects resulting from environmental conditions and way of life are public health concerns because of their high prevalence. Because their etiology is unclear, the aim of this study was to analyze the various forms of enamel hypomineralization, and to characterize the genes involved in this process to determine the mechanisms involved in disruptions of amelogenesis. We used bisphenol A (BPA) and fluoride as models; both are commonly encountered in human populations and utilized in dentistry. Wistar rats were chronically exposed to 5 μg/kg/day BPA from day 1 of gestation to day 65 after birth (P65) and 5 mM fluoride from P21 to P65. Resulting enamel defects were comparable to the human enamel pathologies molar incisor hypomineralization (MIH) and dental fluorosis (DF) respectively, and were more severe in rats exposed to both agents than to each agent alone. Large-scale transcriptomic analysis of dental epithelium showed a small group of genes the expression of which was affected by exposure to BPA or NaF. Among the most modulated, many are directly involved in amelogenesis (Amelx, Enam, Klk4, Mmp12, Slc26a4, and Slc5a8), and can be regrouped as forming the "hypomineralization enameloma." Each of these gene expression perturbations may contribute to enamel defects. Exposure to BPA weakens enamel, making it more prone to generate frequent mineralization defects MIH and DF. Our study identifies hypomineralization genes that may enable the use of dental enamel as an early marker of exposure to environmental toxicants because of its unique ability to retrospectively record ameloblast pathophysiology. © 2016 American Society for Bone and Mineral Research.

Human enamel thickness and ENAM polymorphism

The tooth enamel development gene, enamelin (ENAM), showed evidence of positive selection during a genome-wide scan of human and primate DNA for signs of adaptive evolution. The current study examined the hypothesis that a single-nucleotide polymorphism (SNP) C14625T (rs7671281) in the ENAM gene identified in the genome-wide scan is associated with a change in enamel phenotype. African Americans were selected as the target population, as they have been reported to have a target SNP frequency of approximately 50%, whereas non-Africans are predicted to have a 96% SNP frequency. Digital radiographs and DNA samples from 244 teeth in 133 subjects were analysed, and enamel thickness was assessed in relation to SNP status, controlling for age, sex, tooth number and crown length. Crown length was found to increase with molar number, and females were found to have thicker enamel. Teeth with larger crowns also had thicker enamel, and older subjects had thinner enamel. Linear regression and generalized estimating equations were used to investigate the relationship between enamel thickness of the mandibular molars and ENAM SNP status; enamel in subjects with the derived allele was significantly thinner (P=0.040) when the results were controlled for sex, age, tooth number and crown length. The derived allele demonstrated a recessive effect on the phenotype. The data indicate that thinner dental enamel is associated with the derived ENAM genotype. This is the first direct evidence of a dental gene implicated in human adaptive evolution as having a phenotypic effect on an oral structure.

Association of ENAM gene single nucleotide polymorphisms with dental caries in Polish children

Objectives

The objective of this study was to prove the association between dental caries and single nucleotide polymorphisms (SNPs) in the ENAM gene.

Material and methods

The research was carried out in 96 children (48 with caries and 48 counterparts free of this disease), aged 20–42 months, with 11–20 erupted teeth. All children were from four day nurseries located in Poznan. The study included the dental examination to select individuals to the research and oral swab collection for molecular evaluation. Seven selected SNPs markers of the ENAM gene were genotyped, five using TaqMan probe assay (rs2609428, rs7671281, rs36064169, rs3796704, and rs12640848) and two by Sanger sequencing (rs144929717 and rs139228330).

Results

Statistically significant higher prevalence of the alternative G allele and the alternative GG homozygote in the control group in comparison with the caries group in SNP rs12640848 was observed, respectively, p = 0.0062 and 0.0010. Although the prevalence of the AG heterozygote was higher for the caries subjects in comparison with controls (OR = 2.9), and the result was statistically significant (p = 0.0010), the overall prevalence of the G allele for this SNP was significantly higher in control group (OR = 2.3; p = 0.0062).

Conclusions

The study revealed the strong association between rs12640848 marker of ENAM gene and caries susceptibility in primary teeth in children from Poznan.

Clinical relevance

The presence of SNPs in the ENAM gene may be important as suspected predictive factor of dental caries occurrence in children.

Genetic influences on dental enamel that impact caries differ between the primary and permanent dentitions

Clinically, primary and permanent teeth are distinct anatomically and the presentation of caries lesions differs between the two dentitions. Hence, the possibility exists that genetic contributions to tooth formation of the two dentitions are different. The purpose of this study was to test the hypothesis that genetic associations with an artificial caries model will not be the same between primary and permanent dentitions. Enamel samples from primary and permanent teeth were tested for microhardness at baseline, after carious lesion creation, and after fluoride application to verify association with genetic variants of selected genes. Associations were found between genetic variants of ameloblastin, amelogenin, enamelin, tuftelin, tuftelin interactive protein 11, and matrix metallopeptidase 20 and enamel from permanent teeth but not with enamel from primary teeth. In conclusion, our data continue to support that genetic variation may impact enamel development and consequently individual caries susceptibility. These effects may be distinct between primary and permanent dentitions.

Weaker dental enamel explains dental decay

Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution.

ENAM mutations with incomplete penetrance

Amelogenesis imperfecta (AI) is a genetic disease affecting tooth enamel formation. AI can be an isolated entity or a phenotype of syndromes. To date, more than 10 genes have been associated with various forms of AI. We have identified 2 unrelated Turkish families with hypoplastic AI and performed mutational analysis. Whole-exome sequencing identified 2 novel heterozygous nonsense mutations in the ENAM gene (c.454G>T p.Glu152* in family 1, c.358C>T p.Gln120* in family 2) in the probands. Affected individuals were heterozygous for the mutation in each family. Segregation analysis within each family revealed individuals with incomplete penetrance or extremely mild enamel phenotype, in spite of having the same mutation with the other affected individuals. We believe that these findings will broaden our understanding of the clinical phenotype of AI caused by ENAM mutations.